The present disclosure relates generally to hybrid structures and, more specifically, to methods for use in reducing galvanic corrosion within hybrid structures.
Galvanic corrosion refers to an electrochemical process where in electrons are transferred between materials in electrical contact that have different electrode potentials. A galvanic cell generally includes an anode, a cathode, and an electrolyte that couples the anode and cathode together in electrical contact. During operation, electrons from the material with the more active electrode potential (i.e., the anode) are transferred to the material with the less active electrode potential (i.e., the cathode) via the electrolyte. As such, corrosion occurs when the anode material dissolves in the electrolyte and deposits on the cathode.
Recently, at least some known aircraft components have increasingly been fabricated from composite materials such as carbon-fiber-reinforced polymer (CFRP) in combination with metallic materials such as aluminum, titanium, and/or steel. As used herein, the term “metallic” may refer to a single metallic material or a metallic alloy material. The composite materials generally reduce the weight of the aircraft resulting in an increase in the fuel efficiency of the aircraft. In such assemblies, certain metallic materials have a more active electrode potential than the conductive carbon fibers dispersed within the composite materials.
In at least some known aircraft assemblies, metallic components are coupled to CFRP components via a plurality of fasteners. In one known assembly, CFRP-metallic hybrid structures are formed in a process where the metallic components are aligned with the CFRP parts in a predetermined position, and hole locations are drilled based on the predetermined position. The metallic component is then coupled to the CFRP components with fasteners. In such structures, galvanic corrosion may occur if moisture is introduced between the metallic and CFRP components.
Preventing galvanic corrosion generally requires either eliminating and/or suppressing at least one of the elements of the galvanic cell. When the electrolyte is water, one known method to prevent galvanic corrosion is to apply a water resistant sealant between the anode and cathode to substantially prevent the ingress of the electrolyte therebetween. When forming CFRP-metallic hybrid structures, the sealant is generally applied after the hole locations have been determined, which requires the metallic component to be removed in an intermediate step. However, the process described above that includes alignment of the metallic components, fastener hole formation, removal of the metallic components, sealant application, and re-alignment of the metallic components is an inefficient and time-consuming task, and changes in the ambient conditions after the holes have been formed may cause the parts to distort making re-alignment of holes in the metallic parts with the drill holes difficult.